Table 1.

Radial positions of the first peaks of the layer-lines

Type	G−11/G11	G7/G6	G−4/G−5	G3/G1
Lt	0.0195  (0.0195)	0.0135  (0.0134)	0.0090  (0.0091)	0.0075  (0.0082)
Parity	Odd	Odd	Even	Odd
R	0.0195	0.0120	0.0110	0.0035

Layer-lines are specified by G_n, where n indicates the Bessel order. Radial peak positions were measured on x-ray fiber diffraction patterns and are listed in Å⁻¹ unit. The errors are ±0.0003 Å⁻¹ at most. The structurally corresponding Fourier–Bessel components are listed in the same column for the Lt- and R-type and they are indicated in the top row as Lt-type/R-type. Parity indicates the phase difference between the near and far side of the layer line and it is even when the difference is close to 0° and odd when close to 180°. Since the helical symmetry of the R-type is well established, the radial peak positions of the Lt-type layer lines are calculated from those of the R-type layer lines, taking into account the Bessel order of each layer line, and listed in parenthesis. The close match between the observed and calculated radial positions and phase parities confirms that the deduced symmetry of the Lt-type is correct. Only for G₃, the difference between the observed and calculated radial positions is relatively large, probably because of the significant difference in the subunit orientations with respect to the filament axis between the Lt- and R-type structures, but the peak position calculated for G₂ is 0.060, which is twice further than that for G₃.